I need to file for 2014, 15, and 16 but I live overseas.

[DoninGA]

See this IRS website for U.S. Citizens and Resident Aliens Abroad - Filing Requirements - https://www.irs.gov/individuals/international-taxpayers/us-citizens-and-resident-aliens-abroad-filin...

Tax return mailing addresses for international taxpayers - https://www.irs.gov/individuals/international-taxpayers/us-citizens-and-resident-aliens-abroad-where...

To purchase software from the TurboTax website you will need a US credit card with a US billing address.

Each tax year is a separate program.  Go to this TurboTax website to purchase and download a prior tax year (2014 thru 2016) desktop edition - https://turbotax.intuit.com/personal-taxes/past-years-products/

You can also purchase the software from a reputable online retailer, such as Amazon.

Prior year tax returns can only be printed and mailed, they cannot be e-filed.

When mailing multiple tax years you should use a separate envelope for each tax year.